The effect of wheel frequency on chatter was experienced first-hand by the author while developing a process for grinding large-diameter thin-walled casings with vitrified CBN. The project was initially prone to extreme chatter and noise. Maximizing the stiffness and nodal frequency of a steel-cored wheel by reducing the diameter by 30% and then doubling the body width increased wheel life by an order of magnitude and reduced noise by >20 dB. However, subsequently changing the hub material from steel to CFRP of comparable stiffness but one third the density further doubled wheel life. CFRP would have provided some additional damping but also significantly increased the natural frequency of the wheel due to its low density.
4.7.3 Summary
In conclusion, lightweight flexible hubs can provide benefit in grinding by limiting self-excited chatter generation with superabrasive wheels. Damping may also be an issue, but hub compliance and frequency responses are more likely to be the controlling factors. The concept is unlikely to be effective where significant forced vibration is present, although it is sometimes difficult to differentiate the two.
Compliance is much higher in conventional wheels. The effect on contact width for suppressing chatter is particularly pronounced when using plastic bonds for camshaft grinding or shellac bonds for roll grinding. Some benefit is even seen using rubber inserts in the bores of vitrified alox wheels for roll grinding. Even with resin diamond wheels, Busch [1970] was able to show a 300% improvement in life merely by placing a rubber sleeve between the wheel and flange to increase compliance.
Further research is likely to be focused on this aspect of wheel design as superabrasive technology targets applications such as roll and centerless grinding. It should be noted that efforts have been published regarding commercial product introducing microelasticity into vitrified diamond and CBN bonds [Graf 1992]. A more comprehensive review of the whole subject of grinding chatter excluding centerless grinding is given by Inasaki, Karpuschewski, and Lee [2001].